In an initial experiment, pregnant Sprague-Dawley rats were administered CdCl2 on gestation days 12, 13, and 14; control rats received saline. Birth was delayed by 24 hours in CdCl2 treated dams. Placenta, fetal body, and lung weights were not affected by in utero CdCl2 exposure. However, the lungs of fetuses treated in utero contained greater amounts of glycogen than controls. In addition, about 10% of treated pups died within 1 day after birth. When the study was repeated using a larger number of pregnant dams (10 per group), 25% of pups from treated dams died within 24 hours after birth; none of the control pups died. Lungs of treated pups that died had significantly increased levels of glycogen compared to surviving treated and control pups. These preliminary data suggest that in utero exposure to CdCl2 may inhibit surfactant production possibly by interfering with glycogen utilization. In a subsequent study, treatment of pregnant dams with nicotine from gestation day 5 until birth had no effect on fetal lung weights or glycogen depletion, or on survival of neonates.